>> I would like to ask you how you feel about adding the possibility to fade
>> the lines that are not in the center of the attention in the editing area.
I like it a lot. It provides extra cues to focus on the part of the document you are working on, without losing the context. However I would want to see how it behaves in the face of rapid scrolling - when you want to move your point of attention to a different part of the document manually, rather than searching.
It almost gives the impression that the text is wrapped around a large drum, with the nearest lines being most visible.
I also like the idea suggested by someone else, that it be switchable (presumably it can be switched off for those people who don't like it) to provide focus not by number of lines, but by the current document element. (It is hard to know which is going to be best without being able to try it out).
Richard